The present invention relates to a latching mechanism for doors on household appliances and particularly to latching mechanisms that provide assistance in compressing a door gasket or the like.
Appliances such as dishwashers and front-loading washing machines may have an access door with a gasket that must be compressed to seal water within a washing chamber. Small area, highly compliant gaskets may be sealed by pressure from the user during the closing the door. The gasket may then be held in a compressed state by a latch mechanism.
Gaskets which require more force may be compressed by a latch mechanism having a lever operated by the user to engage a catch and draw the catch inward with a lever advantage to compress the gasket and hold the door shut.
A closing lever may be avoided in latch mechanisms that provide an “over-center” spring mechanism. During initial stages of closing of the door, closing force on the door is used to energize a spring. When the door closes past the over-center point, the spring releases its energy in a manner to pull the door fully closed. An example an over-center spring mechanism is described in U.S. Pat. No. 4,497,513 to Sasaki.
A variation on the over-center spring mechanism energizes the spring as the door is opened and holds that energy until the door is closed again. An over-center design is still employed and therefore a slight compression of the spring is required when the door is closed to release the energy. A latch of this kind is disclosed in U.S. Pat. No. 2,833,578 to Burke.
U.S. Pat. No. 6,290,270 to Spiessl shows a variation on Burke in which the latch spring is energized when the door is opened and held in the energized state by the rotation of a cam. When the door is closed, the cam is rotated by a strike to release the energized spring. This design reduces the force required to close the door by eliminating the need to compress an over-center spring mechanism during door closure.
In this latter design, the cam is held on a lever, and the energized spring moves the lever and cam. The spring engages the lever “outboard” of the cam to produce the necessary force over the needed distance with a manageable spring size. The lever in this design provides for a relatively narrow latch but increases the required height of the latch because of the necessary length of the lever and the outboard position of the spring. The lever is subject to significant bending forces making it difficult to implement the lever using injection molded thermoplastic, a material that is otherwise desirable in this application.